.\" $OpenBSD: ehci.4,v 1.12 2014/03/10 12:19:37 mpi Exp $
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.\" Copyright (c) 2001 The NetBSD Foundation, Inc.
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.\" This code is derived from software contributed to The NetBSD Foundation
.\" by Lennart Augustsson.
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.Dd $Mdocdate: March 10 2014 $
.Dt EHCI 4
.Os
.Sh NAME
.Nm ehci
.Nd USB Enhanced Host Controller Interface
.Sh SYNOPSIS
.Cd "ehci* at cardbus?"
.Cd "ehci* at pci?"
.Cd "usb*  at ehci?"
.Sh DESCRIPTION
The
.Nm
driver provides support for the USB Enhanced Host Controller Interface,
which provides an interface to
.Xr usb 4
devices.
.Pp
EHCI controllers are peculiar in that they can only handle the USB 2.0
protocol.
This means that they normally have one or more companion controllers
(i.e.,
.Xr ohci 4
or
.Xr uhci 4 )
or an internal rate-matching hub to handle USB 1.x devices.
.Pp
If at least one companion controller is present, each USB connector is
electrically connected to two USB controllers.
The handling of this is totally automatic,
but can be noticed since USB 1.x and USB 2.0 devices plugged in to the same
connector appear to connect to different USB buses.
.Sh SEE ALSO
.Xr cardbus 4 ,
.Xr ohci 4 ,
.Xr pci 4 ,
.Xr uhci 4 ,
.Xr usb 4
